Research in behavioral economics has indicated that subtle changes in how a choice is presented can have profound effects on the health decisions that people make. One such result is the default effect. For example (Johnson & Goldstein, 2003), organ donation rates are much higher in an opt-out system (presumed consent unless person says otherwise) than in an opt-in system (explicit consent required). Both systems give decision makers the autonomy to choose according to their preferences, but the opt-out system provides a nudge (Thaler & Sunstein, 2008) toward donation. The objective of the current research is to examine the use of default options as a mechanism to encourage healthy behavior in three aging-relevant domains: (i) influenza vaccination, (ii) dietary choices, and (iii) pharmaceutical prescription refills. Field studies in each domain will examine real-life health behavior under both opt-in and opt-out defaults. In the flu shot study, outpatients will be automatically scheduled for a flu shot appointment (with the option to opt out) or not scheduled but have the option to opt in. Actual vaccination status will be tracked, with the prediction that vaccination rates will be higher in the opt-out condition. The dietary choice study will examine coffee purchases in cafis that use different defaults for type of milk. In one sub-study, participants will be given a gift card that pictures either a cappuccino with nonfat milk or a cappuccino with whole milk and sugar syrup. The card serves as the customer's default order: the server will provide that drink unless the customer requests something else. Actual purchases will be observed. In the prescription study, prescriptions at a pharmacy will either be enrolled in an automatic refill program (where the prescription is automatically refilled when it is due) or remain in the usual state where the patient must request a refill from the pharmacy. Timeliness of patient refill pick-ups from the pharmacy will be assessed. These studies may demonstrate that simple changes in how health options are presented can have major effects on health behavior and hence on public health. PUBLIC HEALTH RELEVANCE: The health behavior of individuals has a critical impact on health outcomes such as infectious disease epidemics and chronic diseases including heart disease and diabetes. Older adults are at increased risk for morbidity and mortality from each of these diseases. Simple and subtle changes in the way that health options are presented can have important influences on the health behaviors that individuals choose and hence on public health outcomes.